1. Field of the Invention
The present invention relates to a sheet or film for use for a projection screen, a projection screen, and a projection display device, and a light diffusion sheet or film and a projection screen using the light diffusion sheet or film, each of which is suitable for being viewed by having obliquely projected thereon an image from an image light source having a cell structure such as an LCD (Liquid Crystal Display Device), or a DMD (Digital Micro-mirror Device).
2. Description of the Related Art
A rear-surface projection type projection display device using three CRTs of red, green, and blue as the image light source and using a transmission type projection screen as the projection screen is conventionally known. In general, the projection screen is constructed using a Fresnel lens sheet and a lenticular lens sheet, and it is the projection screen that is for the purpose of obtaining a diffusion surface having directionality by causing an image to be focused thereon through the use of an image light from a projector. And, as illustrated in FIG. 10, the projection screen 80 has a Fresnel lens sheet 81 having formed on the light emission or outgoing side a circular type Fresnel lens 81b and a lenticular lens sheet 82 that is disposed on the viewer side of that Fresnel lens 81 and has formed on the light incidence side a horizontal diffusion lenticular lens and has formed on the light emission side a black stripe.
And, the Fresnel lens has formed in the acrylic material at prescribed pitches grooves each of that has a prescribed angle and thereby has a function to condense onto the front surface the light rays that have been diffused from the image light in the form of radial rays.
Also, the lenticular lens is the one for obtaining principally a diffused light having directionality in the horizontal direction and has its cylindrical lenses regularly formed in one flat plane in the longitudinal direction lenses to thereby have a function to spread the light distribution property in the horizontal direction.
The projection screen that is used therein, ordinarily, is also only suitable for the projection in the parallel direction in regard to the projection method as well. Generally, for the projection of an image light with respect to the projection screen, the method is adopted that maximizes the focal distance by the use of a reflection mirror. However, in recent years, it has been being observed that the use purpose of the projection screen is increasing in number to a wide variety of use purposes for having people view an image that uses the projection screen. Following this, in regard to the projection method as well, there has been an increasing demand for a projection display device, etc. wherein an image is viewed by projecting the image directly onto the projection screen by projecting from an image light source having a cell structure such as an LCD, a DMD, etc.
If with the conventional system an image is obliquely projected onto the projection screen from the image light source as described above, the difference in size and shape, or the like, between the upper and the lower of the letter of the projected image on the projection screen occurs. This raised the basic problem that the image is very difficult for the viewer to see. For that reason, there had been made at a lot of quarters attempts to provide a projection screen and system enabling viewing by obliquely projecting the image onto the projection screen without lowering the quality level of the image, as one type of projection display device. Under these circumstances, the inventor of this application disclosed in the specification of his Japanese Patent Application Laid-Open No. 2000-180967 a projection screen and a projection display device that is a projection system which in a rear-surface projection type display upwardly or downwardly projects the image from an image light source toward the projection screen while maintaining the quality of the image at a level equal to that which is attained when projecting the image from the image light source in parallel directions with one another and in which a total-reflection prism is provided on the light incidence surface side of the projection screen.
However, since the above-described projection screen necessitates two sheets of lens systems,it is necessary to provide two production lines for manufacturing those respective lenses and, in addition, the operations for handling could not help becoming complicated. Also, since using a circular Fresnel lens or a circular-arc-like prism, there is the problem that continuous production is difficult.
Whereupon, a first object of the present invention is to provide a sheet or film for use for a projection screen, the projection screen, and a projection display device, and a production method for the sheet or film for use for the projection screen and the projection screen, each of which enables making the handling simple and also enables the performance of continuous production by a single production line.
On the other hand, regarding the projection display device, etc., for the purpose of enhancing the level of the viewer""s visual recognition, the one wherein the light diffusion or film is used for the screen is known. As the light diffusion sheet or film, there are, for example, the one wherein concavities/convexities processing is performed on the surface of a light transmission film, the one wherein light diffusion fine particles are contained in the interior of a resin film, a lenticular lens sheet wherein circular-columnar lenses are parallel-disposed in one flat plane, etc. Also, the using of those sheets in combination two or three in number has also been performed. Each of those projection display devices is the one that aims to enhance the visual recognition by, utilizing the difference between the respective indexes of refraction of the film, the atmospheric air, the fine particles, etc., refracting the image light at the boundaries thereof in many directions, diffusing the image light into a wide range of area, and thereby causing it toward the viewer side.
However, that results in that by the sheet surface having formed thereon the light diffusion fine particles or the concavities and convexities the image light has been randomly reflected to cause the occurrence of many stray lights, followed by deterioration in the surface brightness, contrast, etc. of the display. Also, the light diffusion sheet or film that has the diffusion properties as a result of the concavities/convexities processing of the surface, because that diffusion property and transparency property have angle dependency, had the problem that the visual recognition varies depending upon the angle at which the viewer watches the screen. On the other hand, the light diffusion property of the light diffusion sheet or film leads also to increasing the scatter reflection of the external light, with the result that the contrast remarkably decreases, raising the problem that the image becomes likely to be out of focus. On that account, the present invention has a second object to provide a light diffusion sheet or film wherein the surface brightness does not decrease, nor does the contrast deteriorate; the angle dependency is less; and the scatter reflection of the external light is less, and a projection screen using that light diffusion sheet or film.
Further, in the above-described construction, there is the problem that the external light that had entered from the light outgoing surface side has been reflected by the incidence surface of the sheet, followed by the deterioration in the contrast. In addition, when attempting to cause the procurement of the properties with use only of the above-described random diffusion and the diffusion in the one-side surface lens, the upper limit of the gain is only to an extent of 3 and it is impossible to obtain a gain greater that that. On that account, the present invention has a third object to provide a light diffusion sheet or film that can prevent the reflection of external light that has entered from the light emission surface and thereby obtain a high value of gain, and a projection screen using that light diffusion or film.
On the other hand, in the liquid crystal display device, or the like, there is known the one wherein, for enhancing the viewer""s visual recognition, a light diffusion sheet is used on the viewer side of the liquid crystal panel. For that light diffusion sheet, there are, for example, the one that is obtained by performing concavity/convexity processing with respect to the surface of a light transmission film, the one wherein light diffusion fine particles are contained in the resin film, a lenticular lens sheet wherein circular-columnar lenses are disposed in parallel with one another on one flat surface, etc. Also, using these sheets two or three in number in combination has been being done, too. Each of these is intended to enhance the visual recognition properties by, utilizing the difference between the refractive indexes of the film, the atmospheric air, the fine particles, etc., refracting the image light rays at the boundary between each two of them in many directions, thereby diffusing the image light rays over a wide range, and making them go out toward the viewer side.
However, that results in that, by the surface of the sheet having formed thereon the light diffusion fine particles, concavities/convexities, etc., the image light rays were randomly reflected to cause the occurrence of a lot of stray light rays, followed by the decrease in the surface brightness and contrast of the display. Also, the light diffusion sheet that has the diffusion properties through the performance of the concavities/convexities processing on the surface has its diffusion properties and transparency change depending upon the angle. Therefore, there is the problem that the visual recognition properties changed according to the angle from that the display has been viewed. On the other hand, the light diffusion properties of the light diffusion sheet lead also to increasing the scatter reflection of the external light and this remarkably decreases the contrast, raising the problem that the image easily gets out of focus. In a case where using a single light diffusion sheet independently, there is also the problem that the enlargement of the angle of visibility in the horizontal, or perpendicular, direction became insufficient.
On that account, the present invention has a fourth object to provide a member with an enlarged two-dimensional angle of visibility, that prevents the decrease in the surface brightness and that of the contrast due to the stray light rays, has less dependency upon the angle, and has the external light rays less scatter reflected, and a display device using that member with an enlarged two-dimensional angle of visibility.
Hereinafter, the present invention will be explained.
In a first aspect of the present invention, the above object is solved by providing a sheet or film for use for a projection screen, the sheet or film being adapted to be used for a screen of a rear surface projection type projection display device and be equipped with a prism surface and a lenticular lens surface, wherein the prism surface and the lenticular lens surface are formed integrally with each other in the way in which their respective reverse surfaces are bonded together; the prism surface is formed, as a total reflection linear Fresnel lens, on at least a part of an image light source side of the display device; and the lenticular lens surface is formed on a viewer side of the linear Fresnel lens in the way in which its cross section is in the shape of a trapezoid.
According to this first aspect of the present invention, since the projection screen that has been conventionally constructed of two lens sheets can be constructed of a single sheet of lens, the number of production processes can be reduced and therefore the productivity can greatly be enhanced. Resultantly, the invention can contribute to achieving the cost-down of the product. Also, in case comparison is made with the construction that is made up of two sheets of lenses, the invention is also advantageous from the viewpoint of the transmittance. Also, since the lens assembly is comprised of the linear Fresnel lens and the lenticular lens the cross section of that is trapezoidal, continuous manufacture thereof on the production line becomes possible. From this viewpoint as well, it is possible to greatly enhance the productivity.
In the above-described aspect of the invention, the angle defined by one slant of the trapezoid of the lenticular lens may be formed in the way of being made different in the width direction thereof so that the optical axis, as viewed in the horizontal direction, of an image light may be corrected.
If that is done like that, the optical-axial correction in the horizontal direction and therefore it is possible to provide an excellent image to the viewers.
Also, in this aspect of the invention, on the viewer side of the slant of the trapezoid there may be disposed a material having a refractive index lower than the refractive index of a material constituting the trapezoid. In this case, the material having a low refractive index may be constructed of a solid, liquid, or gaseous one regardless of whether it is solid, liquid, or gaseous. In addition, that material needs only to be adhered substantially onto the entire surface of the slant of the trapezoid. Accordingly, that material may be filled on the whole surface of the xe2x80x9cVxe2x80x9d-shaped groove intervening between two adjacent of the trapezoids or on a part of the surface thereof.
If the invention is constructed like that, the light rays that go through the lenticular lens toward the viewer are for the most part reflected by the slant of the trapezoid. As a result of this, it is possible to obtain a light diffusion in the horizontal direction and hence it becomes possible to ensure a large angle of visibility in the horizontal direction.
In a case where the invention is constructed like that, further, it may be arranged that the material having a lower refractive index be colored. And, the material having a lower refractive index may be colored by adding dye, pigment, or light absorption particles.
In a case where the invention is constructed like that, even when there is a light that has transmitted through the slant of the trapezoid without being reflected by it, it can be absorbed into within the colored low refractive index material. Also, coloring can be achieved by adding to the low refractive index material various kinds of materials including dye, pigment, light absorption particles, etc.
In the above-described first aspect of the invention, on the viewer side of the slant of the trapezoid there may be formed a layer consisting of a low refractive index material having a refractive index lower than the refractive index of a material constituting the trapezoid.
If that is done like this, the amount of the low refractive index material can be mitigated, thereby enabling the reduction in the weight of the screen. Also, it is possible to further form a third layer on the layer of the low refractive index material, thereby imparting a desired function.
Also, on the viewer side of the low refractive index material there may be provided a light absorption portion. In this case, that light absorption portion may be provided by providing on the viewer side of the layer of the low refractive index material a black stripe, for example, with the use of a black color painting.
If doing this, even when there is a light that has transmitted without being reflected by the slant of the trapezoid, that light can be absorbed by the light absorption portion, whereby the same effect as that obtainable when coloring the low refractive index material can be obtained.
Further, it may be arranged that on the viewer side of the slant of the trapezoid there be formed a reflection layer of metal.
In a case where doing like that, it is possible to almost completely reflect the light that is going to transmit the slant of the trapezoid from inside the lenticular lens regardless of the index of refraction of the material that is disposed on the viewer side of the slant of the trapezoid.
Also, the invention may be constructed as a sheet or film for use for the projection screen wherein on the viewer side of the sheet or film for use for the projection screen according to the above-described aspect there is further provided a diffusion layer.
If constructing like that, the diffusion in both the horizontal direction and the vertical direction of the screen is compensated for, with the result that the uniformity of the image can be improved.
In a second aspect of the present invention, the above object is solved by providing a projection screen wherein on the viewer side of the sheet or film for use for the projection screen according to the above-described aspect of the invention there is further provided a diffusion sheet.
According to the second aspect of the present invention, it is possible to use in the projection screen the sheet or film for use for the projection screen having the effect attainable with the above-described first aspect of the invention. In addition, the diffusion in both the horizontal and vertical directions of the screen is compensated for by the diffusion sheet, thereby enabling further improvement of the image in terms of the uniformity.
In the above-described aspect, the invention may be constructed in the way in which on the viewer side there is provided at least one function selected from the group consisting of an AR, a HC, an AS, an AG, a soil-resistant function, and a sensor. Here, the xe2x80x9cARxe2x80x9d is an abbreviation of the anti-reflection and is referred to as the function to suppress the reflectance of the light entering the surface of the lens. Also, the xe2x80x9cHCxe2x80x9d is an abbreviation of the hard coat and is referred to as the wear-resisting function to prevent the formation of scratches or claws on the surface of the lens by having the strength of the surface of the lens increased. The xe2x80x9cASxe2x80x9d is an abbreviation of the anti-static and is referred to as the anti-static function. Also, the xe2x80x9cAGxe2x80x9d is an abbreviation of the anti-glare and is referred to as the anti-glare function of the lens. The xe2x80x9csoil-resistant functionxe2x80x9d is referred to as the function to prevent soil from attaching onto the surface of the lens. And, the xe2x80x9csensorxe2x80x9d is referred to, for example, as a touch sensor. In the present invention, it may be made to have only one function, or have multiple functions, of such functions.
In a case where doing like that, it is possible to make the projection screen have a third function to thereby make the product attractive to the demanders.
In a third aspect of the present invention, the above object is solved by a projection display device equipped with the projection screen according to the second aspect of the invention.
If doing like that, the projection screen having the above-described effect can be applied to the projection display device.
In a fourth aspect of the present invention, the above object is solved by a production method of producing a sheet or film for use for a projection screen which comprises: a step of continuously forming a linear Fresnel lens in the longitudinal direction on one-surface side of a base sheet; and a step of continuously forming a lenticular lens, the cross section of that is trapezoidal, on the-other-surface side of the base sheet. Also, in a fifth aspect of the present invention, the above object is solved by providing a production method of producing a projection screen, which comprises: a step of continuously forming a linear Fresnel lens on one-surface side of a base sheet; a step of continuously forming a lenticular lens, the cross section of that is trapezoidal, in the longitudinal direction on the-other-surface side of the base sheet; and a step of bonding a light diffusion sheet on a surface of the continuously formed lenticular lens.
According to the production method of those fourth and fifth aspects of the invention, the sheet or film for use for the projection screen, and the projection screen, can be produced on the continuous production line and therefore the productivity is remarkably increased, and, also, a large reduction in the manufacturing cost can be achieved.
A light diffusion sheet or film according to a sixth aspect of the present invention is the one having formed thereon a plurality of unit lenses one-dimensionally or two-dimensionally, wherein the unit lens is substantially trapezoidal in cross section; the lower bottom of the trapezoid is made to be a light incidence portion and the upper bottom thereof is made to be a light emission portion; and the unit lens is formed using a material having a prescribed refractive index of N1; a portion, the cross section of that is triangular, and that is located between adjacent two of the unit lenses, is formed using a material having a refractive index N2 lower than the N1 and having added thereto light absorption particles; and when it is assumed that xcex8 represents the angle defined by the slant of the trapezoid with respect to a normal line to the light emission portion, the relationship holds true that is expressed as:
sin(90xc2x0xe2x88x92xcex8) greater than N2/N1
and
N1 less than 1/sin 2xcex8
Also, a light diffusion sheet or film according to a seventh aspect of the present invention is the one having formed thereon a plurality of unit lenses one-dimensionally or two-dimensionally, wherein the unit lens is substantially trapezoidal in cross section; the lower bottom of the trapezoid is made to be a light incidence portion and the upper bottom thereof is made to be a light emission portion and is formed using a material having a prescribed refractive index N1; the portion of the slant of the trapezoid has formed thereon a transparent low refractive index layer having a refractive index of N2 lower than the N1; a portion, the cross section of that is triangular, and that is located between adjacent two of the unit lenses, is formed using a material having a refractive index higher than the N2 and having added thereto light absorption particles; and when it is assumed that xcex8 represents the angle defined by the slant of the trapezoid with respect to a normal line to the light emission portion, the relationship holds true that is expressed as:
sin(90xc2x0xe2x88x92xcex8) greater than N2/N1
and
N1 less than 1/sin 2xcex8
In this aspect of the invention, since the cross-sectional configuration of the unit lens is substantially trapezoidal, the xcex8 is constant, namely the slant basically is in the shape of a straight line. However, the present invention includes a case where the slant is curvilinear or in the form of a combination comprised of multiple straight lines each two of that defines a shallow angle. In this case, although the xcex8 varies, if 90% or more of the xcex8 at each portion constituting the slant satisfies the above-described relationship, the below-mentioned effect can be brought about. Therefore that case should be construed as being included in the technical concept of the present invention (The same applies to the xcex8 in the following description.).
According to the light diffusion or film of the sixth and the seventh aspect of the invention, the incident light parallel with the normal line to the light emission surface is totally reflected by the slant of the cross-sectionally viewed trapezoid and is not reflected at all by the light emission surface and instead goes toward the viewer side. Also, the stray light within the sheet or the light that has entered from the viewer side is absorbed by the light absorption particles. Especially, since, in the present invention, the entire cross-sectionally viewed triangle portion is not constructed using the light absorption particles but is constructed using a material wherein the light absorption particles are diffused into the transparent material, the total reflection at the slant portion can be highly efficiently made. Accordingly, it is possible to obtain a light diffusion sheet or film the brightness and contrast of that are respectively high. In addition, the total reflection at the slant portion and the light absorption of the cross-sectionally viewed triangle portion can be realized by being made compatible at a high level, without being affected by the coloring concentration for a material capable of absorbing light.
The screen of the present invention is for use for a single-light-source projector, and, on account of using the Fresnel lens, the angle of incidence upon the present sheet can be made perpendicular. Incidentally, it is known that the angle of incidence upon the slant is generally in a range of 0xc2x0xc2x110xc2x0.
A light diffusion sheet or film according to an eighth aspect of the present invention is the one having formed thereon a plurality of unit lenses one-dimensionally or two-dimensionally, wherein the unit lens is substantially trapezoidal in cross section; the lower bottom of the trapezoid is made to be a light incidence portion and the upper bottom thereof is made to be a light emission portion; and a portion, the cross section of that is triangular, and that is located between adjacent two of the unit lenses, is formed using a material having a refractive index lower than that of the unit lens and having added thereto light absorption particles; and when it is assumed that T represents the length of the upper bottom of the trapezoid; H represents the height of the upper bottom thereof; and xcex8 represents the angle defined by the slant of the trapezoid with respect to a normal line to the light emission portion, the relationship holds true that is expressed as:
0 less than H less than T/(tan(2xcex8+10xc2x0)xe2x88x92tan xcex8)
A light diffusion sheet or film according to a ninth aspect of the present invention is the one having formed thereon a plurality of unit lenses one-dimensionally or two-dimensionally, wherein the unit lens is substantially trapezoidal in cross section; the lower bottom of the trapezoid is made to be a light incidence portion and the upper bottom thereof is made to be a light emission portion; the portion of the slant of the trapezoid has formed thereon a transparent low refractive index layer having a refractive index lower than that of the unit lens; a portion, the cross section of that is triangular, and that is located between adjacent two of the unit lenses, is formed using a material having a refractive index higher than that of the transparent low refractive index and having added thereto light absorption particles; and when it is assumed that T represents the length of the upper bottom of the trapezoid; H represents the height of the upper bottom thereof; and xcex8 represents the angle defined by the slant of the trapezoid with respect to a normal line to the light emission portion, the relationship holds true that is expressed as:
0 less than H less than T/(tan(2xcex8+10xc2x0)xe2x88x92tan xcex8)
According to the light diffusion sheet or film of these eighth and ninth aspects, even a light that has entered at a 10xc2x0 degree angle of inclination at maximum with respect to the normal line to the light emission surface and that has been reflected by the surface of the transparent low refractive index layer of the trapezoid slant formed by the cross section of the unit lens is made to go out from the light emission surface toward the viewer side without reaching the transparent low refractive index layers of the trapezoid slants formed by adjacent two of the cross sections of the unit lenses. Also, the stray light within the sheet or the light that has entered from the viewer side is absorbed by the light absorption particles. In the present invention as well, the entire cross-sectionally viewed triangle portion is not constructed using the light absorption particles but is constructed using a material wherein the light absorption particles are diffused into the transparent material, the total reflection at the slant portion can be highly efficiently made. Accordingly, it is possible to obtain a light diffusion sheet or film the brightness of that is high and the stray light of that is less.
A light diffusion sheet or film according to a tenth aspect of the present invention is the one having formed thereon a plurality of unit lenses one-dimensionally or two-dimensionally, wherein the unit lens is substantially trapezoidal in cross section; the lower bottom of the trapezoid is made to be a light incidence portion and the upper bottom thereof is made to be a light emission portion; and the unit lens is formed using a material having a prescribed refractive index of N1; a portion, the cross section of that is triangular, and that is located between adjacent two of the unit lenses, is formed using a material having a refractive index N2 lower than the N1 and having added thereto light absorption particles; and when it is assumed that T represents the length of the upper bottom of the trapezoid; H represents the height of the upper bottom thereof; and xcex8 represents the angle defined by the slant of the trapezoid with respect to a normal line to the light emission portion, the relationship holds true that is expressed as:
sin(90xc2x0xe2x88x92xcex8) greater than N2/N1
N1 less than 1/sin 2xcex8
and
0 less than H less than T/(tan(2xcex8+10xc2x0)xe2x88x92tan xcex8)
Also, a light diffusion sheet or film according to an eleventh aspect of the present invention is the one having formed thereon a plurality of unit lenses one-dimensionally or two-dimensionally, wherein the unit lens is substantially trapezoidal in cross section; the lower bottom of the trapezoid is made to be a light incidence portion and the upper bottom thereof is made to be a light emission portion; and the unit lens is formed using a material having a prescribed refractive index of N1; the portion of the slant of the trapezoid has formed thereon a transparent low refractive index layer having a refractive index of N2 lower than the N1; a portion, the cross section of that is triangular, and that is located between adjacent two of the unit lenses, is formed using a material having a refractive index higher than the N2 and having added thereto light absorption particles; and when it is assumed that T represents the length of the upper bottom of the trapezoid; H represents the height of the upper bottom thereof; and xcex8 represents the angle defined by the slant of the trapezoid with respect to a normal line to the light emission portion, the relationship holds true that is expressed as:
sin(90xc2x0xe2x88x92xcex8) greater than N2/N1
N1 less than 1/sin 2xcex8
and
0 less than H less than T/(tan(2xcex8+10xc2x0)xe2x88x92tan xcex8)
This light diffusion sheet or film according to the tenth and the eleventh aspect of the present invention has the merits of the seventh and the ninth aspect as well as the sixth and the eighth aspect of the present invention. According to each of these light diffusion sheet or film, the incident light rays that are parallel with the normal line to the light emission surface are totally reflected by the surface of the transparent low refractive index layer of the slant and, at the light emission surface, are made to go out toward the viewer side without undergoing the total reflection. Also, even a light that has entered at a 10 degrees angle of inclination at maximum with respect to the normal line to the light emission surface and that has been reflected by the surface of the transparent low refractive index layer of the trapezoid slant formed by the cross section of the unit lens is made to go out from the light emission surface toward the viewer side without reaching the transparent low refractive index layers of the trapezoid slants formed by adjacent two of the cross sections of the unit lenses. In the present invention as well, the entire cross-sectionally viewed triangle portion is not constructed using the light absorption particles but is constructed using a material wherein the light absorption particles are diffused into the transparent material. Therefore, the total reflection at the slant portion can be highly efficiently made. Accordingly, it is possible to obtain a light diffusion sheet or film the brightness and contrast of that are high and the stray light of that is less.
In the light diffusion sheet or film of the tenth aspect of the present invention, it may be constructed in the way in which the prescribed refractive indexes N1 and N2 and the length T and height H of the upper bottom of the trapezoid satisfy the relationship of:
1 less than N1 less than 5.76
0.23 less than N2/N1 less than 0.996
and
xe2x80x83H less than T/0.57
This modification can also be suitably applied to the light diffusion or film of each of the sixth to the eleventh aspect, independently, or in a form combined with other modifications.
In a case where the invention is constructed like that, in the light diffusion or film according to the tenth aspect of the invention, when the xcex8 is in a range of 5xc2x0 to 15xc2x0, the incident light rays that are parallel with the normal line to the light emission surface can be totally reflected by the slant surface and at the light emission surface can be made to go out toward the viewer side without the occurrence of reflection. Also, once it has been reflected within the sheet by the slant surface, the light is made to go out from the light emission surface without reaching another slant surface again. Here, the reason why the range of the xcex8 has been set to 5xc2x0 to 15xc2x0 is because a suitable angle of visibility characteristic can be obtained by making the taper angle of the unit lens range from 5xc2x0 to 15xc2x0.
In the light diffusion sheet or film of the seventh aspect, the thickness of the transparent low refractive index layer may be 0.1 xcexcm or more. This modification can also be suitably applied to the light diffusion or film of the sixth to the eleventh aspect, independently, or in a formed combined with other modifications.
If doing like that, it is possible to make the total reflection resulting from the transparent low refractive index layer reliable. Also, in the light diffusion sheet or film according to the sixth aspect, the amount of the light absorption particles added to the material forming the portion the cross section of that is triangular may be between 10 and 60 mass %. The amount of the light absorption particles more preferably is between 30 and 50 mass %. This modification can also be suitably applied to the light diffusion or film of the sixth to the eleventh aspect, independently, or in a formed combined with other modifications.
In a case where constructing like that, it is possible to make the addition effect of the light absorption particles maximum. When the amount added is smaller than that, the amount filled into the cross-sectionally viewed triangle portion becomes deficient and resultantly the width of the so-called black stripe becomes narrow, which results in that the contrast deteriorates. Also, if adding in an amount larger than that, it is unpreferable because the light absorption particles inconveniently remain on the light emission surface (the upper bottom portion of the trapezoid).
Also, in the light diffusion sheet or film according to the sixth aspect, the average particle size of the light absorption particles may be from {fraction (1/30)} to ⅔, or more preferably from {fraction (1/20)} to ⅓, of the height, or the opening width of the groove, of the light emission portion forming the upper bottom of the cross-sectionally viewed trapezoid. This modification can also be suitably applied to the light diffusion or film of the sixth to the eleventh aspect, independently, or in a formed combined with other modifications.
By doing so, the light absorption effect can be made high inefficiency. In addition, when manufacturing, it can be filled into the cross-sectionally viewed triangle portion without any problem coming up. In a case where making the particle size larger than necessary, the particles inconveniently protrude from the defining line of the triangle portion without being sufficiently buried within that triangle portion, with the result that it becomes more likely that clearances are produced. Conversely, in a case where the particle size is smaller than necessary, although the filling into the triangle portion becomes easier, it becomes difficult at the time of manufacture to scratch the light absorption particles off from the light emission surface. Resultantly, the tendency becomes higher that the light absorption particles remain on the light emission surface of the lens.
Also, in the light diffusion sheet or film according to the sixth aspect of the invention, the light emission portion may be formed in the way of being made convex toward the viewer side. This modification can also be suitably applied to the light diffusion or film of the sixth to the eleventh aspect, independently, or in a formed combined with other modifications.
If doing so, the light absorption particles are prevented from being left on the light emission portion at the time of manufacture. Therefore, such is convenient.
Also, in the light diffusion sheet or film according to the sixth aspect, the unit lens may be formed on a plate-like, or a film-like, transparent base member. This modification can also be suitably applied to the light diffusion or film of the sixth to the eleventh aspect, independently, or in a formed combined with other modifications.
In a case where having done so, it is possible, using the die roll, to perform manufacture of the arrayed unit lenses continuously.
Also, in the light diffusion sheet or film according to the sixth aspect, it may have bonded thereto on the viewer side a sheet having mixed therein a diffusion agent.
In a case where having done so, since the surface on the viewer side can be made a flat plane, machining with respect to the obverse surface becomes easy. Also, owing to the optical action of the diffusion agent, the gain on the light emission side can be uniformly leveled. The index of refraction of a bond layer or adhesion layer for bonding that diffusion agent-mixed sheet may be approximately the same as that of the unit lens. This is because it is thought that no adverse effects as optically viewed exist.
In a case where having constructed as mentioned above, on the viewer side of the diffusion agent-mixed sheet there may be provided at least one of an anti-reflection layer, a hard coat layer, a polarizing filter layer, an anti-static layer, a glare-proofing layer, a soil-proofing layer, and a touch sensor layer. In the present invention, it may be arranged that only one of those functions be provided on the viewer side, or multiple ones thereof be provided thereon.
In a case where having constructed in a such-like way, the light diffusion sheet or film can be made to have a variety of functions.
Also, further, in the present invention, the above object is solved by providing a projection screen wherein the Fresnel lens is disposed on the image light source side of any one of the light diffusion sheets or films.
According to that the above, the properties of the light diffusion sheet can be realized in the projection screen.
Also, in that projection screen, it may be arranged that the slant of the cross-sectionally viewed trapezoid of each of a plurality of the unit lenses be formed in the way of being extended in the vertical direction.
According to the above, the light can be diffused horizontally.
A light diffusion sheet or film according to a twelfth aspect of the invention is the one having formed thereon a plurality of unit lenses one-dimensionally or two-dimensionally, wherein the unit lens is substantially trapezoidal in cross section; the lower bottom of the trapezoid is made to be a light incidence portion and the upper bottom thereof is made to be a light emission portion; and the unit lens is formed using a material having a prescribed refractive index of N1; a portion, the cross section of that is triangular, and that is located between adjacent two of the unit lenses, is formed using a material having a refractive index of N2 lower than the N1 and having added thereto light absorption particles, or a material having a refractive index of N2 lower than the N1 and having been colored; and when it is assumed that xcex8 represents the angle defined by the slant of the trapezoid with respect to a normal line to the light emission portion, the relationship holds true that is expressed as:
sin(90xc2x0xe2x88x92xcex8) greater than N2/N1
and
N1 less than 1/sin 2xcex8
and the surface of the light incidence portion has performed thereon embossing processing.
Also, a light diffusion sheet or film according to a thirteenth aspect of the invention is the one having formed thereon a plurality of unit lenses one-dimensionally or two-dimensionally, wherein the unit lens is substantially trapezoidal in cross section; the lower bottom of the trapezoid is made to be a light incidence portion and the upper bottom thereof is made to be a light emission portion; and the unit lens is formed using a material having a prescribed refractive index of N1; the portion of the trapezoid slant has formed thereon the transparent low refractive index having a refractive index layer of N2 lower than the N1; a portion, the cross section of that is triangular, and that is located between adjacent two of the unit lenses, is formed using a material having a refractive index higher than the N2 and having added thereto light absorption particles, or a material having a refractive index higher than the N2 and having been colored; and when it is assumed that xcex8 represents the angle defined by the slant of the trapezoid with respect to a normal line to the light emission portion, the relationship holds true that is expressed as:
sin(90xc2x0xe2x88x92xcex8) greater than N2/N1
and
N1 less than 1/sin 2xcex8
and the surface of the light incidence portion has performed thereon embossing processing. Here, since the cross-sectional configuration of the unit lens is substantially trapezoidal, the xcex8 is constant, namely the slant basically is in the shape of a straight line. However, the present invention includes a case where the slant is curvilinear or in the form of a combination of multiple straight lines each two of that defines a shallow angle. In this case, although the xcex8 varies, if 90% or more of the xcex8 at each portion constituting the slant satisfies the above-described relationship, the below-mentioned effect can be brought about. Therefore that case should be construed as being included in the technical concept of the present invention (The same applies to the xcex8 in the following description.).
According to the light diffusion sheet or film according to the twelfth and the thirteenth aspect, since the surface of the light incidence portion is subjected to embossing processing, of the external light rays that have entered from the sheet light emission portion side the light rays that reach the sheet light incidence portion and are reflected are diffused and are incident upon the slant portion at a large angle. Therefore, they enter the cross-sectionally viewed triangle portion without being totally reflected by the slant portion and are absorbed into the light absorption particles or a colored material. This enables enhancing the contrast of the light diffusion or film. Further, the incident light rays that are parallel with the normal line to the light emission surface are totally reflected by the surface of the cross-sectionally viewed trapezoid slant within the light diffusion sheet or film and are emitted toward the viewer side without the occurrence of reflection at the light emission surface. Also, the stray light within the sheet or the light that has entered from the viewer side is absorbed by the light absorption particles or the coloring material. Accordingly, it is possible to obtain a light diffusion sheet or film that has high brightness and contrast.
The screen of the present invention is mainly for use for a single-light-source projector, and, on account of using the Fresnel lens, the angle of incidence upon the present sheet can be made perpendicular. Incidentally, it is known that the angle of incidence upon the slant is generally in a range of 0xc2x0xc2x110xc2x0.
A light diffusion sheet or film according to a fourteenth aspect of the present invention is the one having formed thereon a plurality of unit lenses one-dimensionally or two-dimensionally, wherein the unit lens is substantially trapezoidal in cross section; the lower bottom of the trapezoid is made to be a light incidence portion and the upper bottom thereof is made to be a light emission portion; and a portion, the cross section of that is triangular, and that is located between adjacent two of the unit lenses, is formed using a material having a refractive index lower than that of the unit lens and having added thereto light absorption particles or a material having a refractive index lower than that of the unit lens and having been colored; and when it is assumed that T represents the length of the upper bottom of the trapezoid; H represents the height of the upper bottom thereof; and xcex8 represents the angle defined by the slant of the trapezoid with respect to a normal line to the light emission portion, the relationship holds true that is expressed as:
0 less than H less than T/(tan(2xcex8+10xc2x0)xe2x88x92tan xcex8)
and the surface of the light incidence portion has performed thereon embossing processing.
Also, a light diffusion sheet or film according to a fifteenth aspect of the present invention is the one having formed thereon a plurality of unit lenses one-dimensionally or two-dimensionally, wherein the unit lens is substantially trapezoidal in cross section; the lower bottom of the trapezoid is made to be a light incidence portion and the upper bottom thereof is made to be a light emission portion; the portion of the trapezoid slant has formed thereon a transparent low refractive index layer having a refractive index lower than that of the unit lens; and a portion, the cross section of that is triangular, and that is located between adjacent two of the unit lenses, is formed using a material having a refractive index higher than that of the transparent low refractive index layer and having added thereto light absorption particles or a material having a refractive index higher than that of the transparent low refractive index layer and having been colored; and when it is assumed that T represents the length of the upper bottom of the trapezoid; H represents the height of the upper bottom thereof; and xcex8 represents the angle defined by the slant of the trapezoid with respect to a normal line to the light emission portion, the relationship holds true that is expressed as:
0 less than H less than T/(tan(2xcex8+10xc2x0)xe2x88x92tan xcex8)
and the surface of the light incidence portion has performed thereon embossing processing.
According to the light diffusion sheet or film according to the fourteenth and fifteenth aspect, since the surface of the light incidence portion is subjected to embossing processing, of the external light rays that have entered from the sheet light emission portion side the light rays that reach the sheet light incidence portion and are reflected are diffused and are incident upon the slant portion at a large angle. Therefore, they enter the cross-sectionally viewed triangle portion without being totally reflected by the slant portion and are absorbed into the light absorption particles or the colored material. This enables enhancing the contrast of the light diffusion or film. Further, even the incident light rays that enter the light diffusion sheet or film at a 10 degrees angle of inclination at maximum as defined with respect to the light emission surface and that have been reflected by the surface of the transparent low refractive index layer of the trapezoid slant formed by the cross section of the unit lens are made to go out from the light emission surface toward the viewer side without reaching the transparent low refractive index layer of the trapezoid slant formed by the cross sections of two adjacent of the unit lenses. Also, the stray light within the sheet or the light that has entered from the viewer side is absorbed by the light absorption particles or the colored material.
A light diffusion sheet or film according to a sixteenth aspect of the present invention is the one having formed thereon a plurality of unit lenses one-dimensionally or two-dimensionally, wherein the unit lens is substantially trapezoidal in cross section; the lower bottom of the trapezoid is made to be a light incidence portion and the upper bottom thereof is made to be a light emission portion; and the unit lens is formed using a material having a prescribed refractive index of N1; a portion, the cross section of that is triangular, and that is located between adjacent two of the unit lenses, is formed using a material having a refractive index N2 lower than the N1 and having added thereto light absorption particles, or a material having a refractive index N2 lower than the N1 and being colored; and when it is assumed that T represents the length of the upper bottom of the trapezoid; H represents the height of the upper bottom thereof; and xcex8 represents the angle defined by the slant of the trapezoid with respect to a normal line to the light emission portion, the relationship holds true that is expressed as:
sin(90xc2x0xe2x88x92xcex8) greater than N2/N1
N1 greater than 1/sin 2xcex8
and
0 less than H less than T/(tan(2xcex8+10xc2x0)xe2x88x92tan xcex8)
and the surface of the light incidence portion has performed thereon embossing processing.
A light diffusion sheet or film according to a seventeenth aspect of the present invention is the one having formed thereon a plurality of unit lenses one-dimensionally or two-dimensionally, wherein the unit lens is substantially trapezoidal in cross section; the lower bottom of the trapezoid is made to be a light incidence portion and the upper bottom thereof is made to be a light emission portion; and the unit lens is formed using a material having a prescribed refractive index of N1; the portion of the trapezoid slant has formed thereon a transparent low refractive index layer having a refractive index N2 lower than the N1; a portion, the cross section of that is triangular, and that is located between adjacent two of the unit lenses, is formed using a material having a refractive index higher than the N2 and having added thereto light absorption particles, or a material having a refractive index higher than the N2 and being colored; and when it is assumed that T represents the length of the upper bottom of the trapezoid; H represents the height of the upper bottom thereof; and xcex8 represents the angle defined by the slant of the trapezoid with respect to a normal line to the light emission portion, the relationship holds true that is expressed as:
sin(90xc2x0xe2x88x92xcex8) greater than N2/N1
N1 less than 1/sin 2xcex8
and
0 less than H less than T/(tan(2xcex8+10xc2x0)xe2x88x92tan xcex8)
and the surface of the light incidence portion has performed thereon embossing processing.
The light diffusion sheet or film according to each of the sixteenth and the seventeenth aspect also has concurrently the merits that are obtained with each of the twelfth and the fourteenth, and the thirteenth and the fifteenth aspect of the invention. According to each of those light diffusions or films, since the surface of the light incidence portion is subjected to embossing processing, of the external light rays that have entered from the sheet light emission portion side the light rays that reach the sheet light incidence portion and are reflected are diffused and are incident upon the slant portion at a large angle. Therefore, they enter the cross-sectionally viewed triangle portion without being totally reflected by the slant portion and are absorbed into the light absorption particles or the colored material. This enables enhancing the contrast of the light diffusion or film. Further, the incident light rays that are parallel with the normal line to the light emission surface are totally reflected by the transparent low refractive index layer surface of the trapezoid slant and are emitted toward the viewer side without the occurrence of reflection at the light emission surface. Also, the light that has entered the light diffusion sheet or film at a 10 degrees angle of inclination at maximum with respect to the normal line to the light emission surface and that has been reflected by the surface of the transparent low refractive index layer of the trapezoid slant formed by the cross section of the unit lens is made to go out from the light emission surface toward the viewer side without reaching the transparent low refractive index layers of the trapezoid slants formed by adjacent two of the cross sections of the unit lenses. Accordingly, it is possible to obtain a light diffusion sheet or film the brightness and contrast of that are respectively high and the stray light of that is less.
In the light diffusion sheet or film according to the sixteenth aspect, it may be arranged that T representing the length of the upper bottom of the trapezoid, H representing the height of the upper bottom thereof, and xcex8 representing the angle defined by the slant of the trapezoid with respect to a normal line to the light emission portion satisfy the relationship which is expressed as:
1 less than N1 less than 5.76
0.23 less than N2/N1 less than 0.996
and
H less than T/0.57
This modification can also be suitably applied to the light diffusion or film according to each of the other aspects that are described in and after the twelfth aspects, independently, or in a form combined with other modifications. In a case where the invention is constructed like that, in the light diffusion or film according to the fifth or the sixth aspect of the invention, when the xcex8 is in a range of 5xc2x0 to 15xc2x0, the incident light rays that are parallel with the normal line to the light emission surface can be totally reflected by the slant surface and at the light emission surface can be made to go out toward the viewer side without the occurrence of reflection. Also, once it has been reflected within the sheet by the slant surface, the light is made to go out from the light emission surface without reaching another slant surface again. Here, the reason why the range of the xcex8 has been set to 5xc2x0 to 15xc2x0 is because a suitable angle of visibility characteristic can be obtained by making the taper angle of the unit lens range from 5xc2x0 to 15xc2x0.
In the light diffusion sheet or film of the thirteenth aspect, the thickness of the transparent low refractive index layer may be 0.1 xcexcm or more. This modification can also be suitably applied to the light diffusion or film according to each of the other aspects that are described in and after the twelfth aspects, independently, or in a form combined with other modifications.
If doing like that, it is possible to make the total reflection resulting from the transparent low refractive index layer reliable.
Also, in the light diffusion sheet or film according to the twelfth aspect, the amount of the light absorption particles added to the material forming the portion the cross section of that is triangular may be between 10 and 60 mass %. The amount of the light absorption particles more preferably is between 30 and 50 mass %. This modification can also be suitably applied to the light diffusion or film according to each of the other aspects that are described in and after the twelfth aspects, independently, or in a form combined with other modifications.
In a case where constructing like that, it is possible to make the addition effect of the light absorption particles maximum. When the amount added is smaller than that, the amount filled into the cross-sectionally viewed triangle portion becomes deficient and resultantly the width of the so-called black stripe becomes narrow, which results in that the contrast deteriorates. Also, if adding in an amount larger than that, the light absorption particles inconveniently remain on the light emission surface (the upper bottom portion of the trapezoid).
Also, in the light diffusion sheet or film according to the twelfth aspect, the average particle size of the light absorption particles may be from {fraction (1/30)} to ⅔, or more preferably from {fraction (1/20)} to ⅓, of the height, or the opening width of the groove, of the light emission portion forming the upper bottom of the cross-sectionally viewed trapezoid. This modification can also be suitably applied to the light diffusion or film according to each of the other aspects that are described in and after the twelfth aspects, independently, or in a form combined with other modifications.
By doing so, the light absorption effect can be made high in efficiency. In addition, when manufacturing, it can be filled into the cross-sectionally viewed triangle portion without any problem coming up. In a case where making the particle size larger than necessary, the particles inconveniently protrude from the defining line of the triangle portion without being sufficiently buried within that triangle portion, with the result that it becomes more likely that clearances are produced. Conversely, in a case where the particle size is smaller than necessary, although the filling into the triangle portion becomes easier, it be comes difficult at the time of manufacture to scratch the light absorption particles off from the light emission surface. Resultantly, the tendency becomes higher that the light absorption particles remain on the light emission surface of the lens.
Also, in the light diffusion sheet or film according to the twelfth aspect of the invention, the light emission portion may be formed in the way of being made convex toward the viewer side. This modification can also be suitably applied to the light diffusion or film according to each of the other aspects that are described in and after the twelfth aspects, independently, or in a form combined with other modifications.
If doing so, the light absorption particles are prevented from being left on the light emission portion at the time of manufacture. Therefore, such is convenient.
Also, in the light diffusion sheet or film according to the twelfth aspect, the unit lens may be formed on a plate-like, or a film-like, transparent base member. This modification can also be suitably applied to the light diffusion or film according to each of the other aspects that are described in and after the twelfth aspects, independently, or in a form combined with other modifications.
In a case where having done so, it is possible, using the die roll, to perform manufacture of the arrayed unit lenses continuously.
Also, in the light diffusion sheet or film according to the twelfth aspect, it may have bonded thereto on the viewer side a sheet having mixed therein a diffusion agent. This modification can also be suitably applied to the light diffusion or film according to each of the other aspects that are described in and after the twelfth aspects, independently, or in a form combined with other modifications. In a case where doing like that, since the surface on the viewer side can be made flat, machining with respect to the surface becomes easy. Also, owing to the optical action of the diffusion agent, the gain on the light emission side can be uniformly leveled. The index of refraction of a bond layer or adhesion layer for bonding that diffusion agent-mixed sheet may be approximately the same as that of the unit lens. This is because it is thought that no great effects as optically viewed exist.
In a case where having constructed as mentioned above, on the viewer side of the diffusion agent-mixed sheet there may be provided at least one of an anti-reflection layer, a hard coat layer, a polarizing filter layer, an anti-static layer, a glare-proofing layer, a soil-proofing layer, and a touch sensor layer. In the present invention, it may be arranged that only one of those functions be provided on the viewer side, or multiple ones thereof be provided thereon.
In a case where having constructed in a such-like way, the light diffusion sheet or film can be made to have a variety of functions.
Also, in the light diffusion sheet or film according to the twelfth aspect of the present invention, the configuration of the section, as sectioned by a plane perpendicular to the light emission surface, of the light incidence surface having performed thereon embossing processing may be in the shape of a chipped piece of an ellipse or/and a chipped piece of a polygon. This modification can also be suitably applied to the light diffusion or film according to each of the other aspects that are described in and after the twelfth aspects, independently, or in a form combined with other modifications.
In a case where constructing like that, the light that has entered from the light emission or outgoing surface side can be reflected by the elliptic or polygonal chipped piece portion and can thereby be made to enter the slant portion with the angle of incidence being made sufficiently large. Accordingly, that light can be absorbed by the light absorption particles inside the slant portion and therefore it is possible to obtain a light diffusion sheet or film the contrast of that is high.
In a case where having constructed like that, further, the components of a light that is diffused 3xc2x0 or more by the emboss configuration the embossing of that is performed on the light incidence surface may be made 20% or more.
In a case where having constructed like that, since many rays of light can be absorbed by the light absorption particles, it is possible to realize a light diffusion sheet or film the contrast of that is high.
Also, further, in the light diffusion sheet or film according to the twelfth aspect, it may be arranged that the area of the embossing performed portion that, when it is assumed that xcfx86 represents the components of the angle defined by the slant of the embossing performed portion with respect to the light incidence surface in the same direction as in the case of the xcex8; and N3 represents the refractive index of the material forming the embossed portion, satisfies the relationship of:
sin(90xc2x0xe2x88x92(sinxe2x88x921(N3*sin(2xcfx86)/N1)+xcex8)) less than N2/N1
be 20% or more of the area of the entire incidence surface. Here, in the equality above, the mark xe2x80x9c*xe2x80x9d (asterisk mark) means to multiply the item before or after it by the item after or before it. For example, xe2x80x9cA*Bxe2x80x9d indicates the product of A and B (hereinafter the same applies).
In a case where satisfying those conditions, the external light that has entered from the light outgoing surface in a direction perpendicular to the light outgoing surface is reflected by the embossed surface and is absorbed into the light absorption particles. Accordingly, by providing the embossed surface satisfying such conditions in an amount that is 20% or more of the entire incidence surface, it is possible to realize a light diffusion sheet or film the contrast of that is high.
Also, the components of the light that is diffused 20% or more can be made 20% or less according to the configuration of the embossed portion the embossing of that has been performed on the light incidence surface.
In a case where doing so, many rays of image light that have entered the light diffusion sheet or film can reach the viewer side without being absorbed into the light absorption particles of the between-lens portion. Accordingly, it is possible to realize a light diffusion sheet or film the transmittance of that is high.
Also, further, in the expression above, it may be arranged that the area of the embossing performed portion that satisfies the relationship:
sin(90xc2x0xe2x88x92(sinxe2x88x921(N3/N1)*sin(xcfx86xe2x88x92sinxe2x88x921(sin xcfx86/N3)))+xcex8)) less than N2/N1
be 20% or less of the area of the entire incidence surface.
In a case where satisfying that relationship, the image light that has entered perpendicularly to the light incidence surface is absorbed into the light absorption particles. Accordingly, by controlling so that the area of the embossing performed portion that satisfies the conditions above may be made 20% or less of the area of the entire incidence surface, it is possible to realize a light diffusion sheet or film the transmittance of that is high.
Also, in the light diffusion or film according to the twelfth aspect, it may be arranged that the pitch at which the embossing processing is performed be {fraction (1/15)} to {fraction (1/1.5)} times as high as the pitch of the light emission surface side unit lens. This modification can also be suitably applied to the light diffusion sheet or film according to each of the other aspects that are described in and after the twelfth aspects, independently, or in a form combined with other modifications.
By constructing like that, it is possible to maximize the effect that is produced by forming the emboss on the side of the light incidence surface. As the merits obtained by having made the emboss pitch fine there can be pointed out the merit that it is possible to prevent the diffusion characteristic from becoming coarse and the merit that it is possible to prevent the occurrence of moirxc3xa9 between the light emission lens and the light incidence lens (emboss).
Further, in the present invention, the above-described objects are solved by providing a projection screen wherein on the image light source side of the light diffusion sheet or film according to any one of the above-described aspects there is disposed a Fresnel lens.
According to that the above aspect, it is possible to realize in the projection screen the various properties of the light diffusion sheet.
Also, in the above-described projection screen, the slant of the cross-sectionally viewed trapezoid of each of a plurality of the unit lenses may be extended in the vertical direction.
In a case where that slant is formed like that, it is possible to diffuse the light in the vertical direction.
The above-described functions and advantages of the present invention will become apparent from the modes of embodiment that will be explained below.